Edelbrock Electric Choke Issue

[Roger P.]

Happy New Year Everyone,
I have waited a good part of the year for this week knowing that I would have some time to do a few odds & ends on the Vette. One thing that I wanted to tackle is a hesitation/stumble upon acceleration from a stop when the car is cold. Sometimes the engine will also bog/surge in second gear as well. Once the engine is warmed up, the issues disappear and the car runs great. I searched the archives and the Internet and determined that my problem is the electric choke on my Edelbrock carburetor. Well, I am now frustrated to the point of wanting to "choke" the carburetor . I first tried adjusting the choke by turning the black cover to the right to keep the choke closed longer, but after eventually turning it all the way to the right, discovered that the choke wasn't working at all. It is wired directly to the fuse block into a spade accessory slot, so I checked to make sure I was getting 12 volts. Much to my surprise, it wasn't getting any power. So I changed it to another slot which, when the key is turned on, provides 12 volts at the block and at the choke. YES... not . Well then, it must be a bad choke, right? Luckily, I found a local performance auto parts store that stocks Edelbrock parts and purchased a new choke (not including the linkage piston housing). Cheap enough, and I assumed it would solve the problem... but I am still having the same issue. What the ?? Anyone have an answer to this puzzle? Do I need a new linkage piston housing? When I turn the black cover/dial from one extreme to the other (lean to rich) with the engine off, the choke valve/blade hardly moves at all. Without the choke and a higher "fast" idle, my car will continue to stumble off the line . Help save my sanity!!

Thank you,
Roger (50141)

[Clem Z.]

Re: Edelbrock Electric Choke Issue

Happy New Year Everyone,
I have waited a good part of the year for this week knowing that I would have some time to do a few odds & ends on the Vette. One thing that I wanted to tackle is a hesitation/stumble upon acceleration from a stop when the car is cold. Sometimes the engine will also bog/surge in second gear as well. Once the engine is warmed up, the issues disappear and the car runs great. I searched the archives and the Internet and determined that my problem is the electric choke on my Edelbrock carburetor. Well, I am now frustrated to the point of wanting to "choke" the carburetor . I first tried adjusting the choke by turning the black cover to the right to keep the choke closed longer, but after eventually turning it all the way to the right, discovered that the choke wasn't working at all. It is wired directly to the fuse block into a spade accessory slot, so I checked to make sure I was getting 12 volts. Much to my surprise, it wasn't getting any power. So I changed it to another slot which, when the key is turned on, provides 12 volts at the block and at the choke. YES... not . Well then, it must be a bad choke, right? Luckily, I found a local performance auto parts store that stocks Edelbrock parts and purchased a new choke (not including the linkage piston housing). Cheap enough, and I assumed it would solve the problem... but I am still having the same issue. What the ?? Anyone have an answer to this puzzle? Do I need a new linkage piston housing? When I turn the black cover/dial from one extreme to the other (lean to rich) with the engine off, the choke valve/blade hardly moves at all. Without the choke and a higher "fast" idle, my car will continue to stumble off the line . Help save my sanity!!

Thank you,
Roger (50141)

does the end of the thermostatic spring in the choke fit into a slot in the choke linkage? a picture of the choke housing showing the linkage would help.

[Roger P.]

Re: Edelbrock Electric Choke Issue

does the end of the thermostatic spring in the choke fit into a slot in the choke linkage? a picture of the choke housing showing the linkage would help.

Clem,
The spring has a "hooked" end that latches on to a short post/stud which is attached to the linkage piston. The post moves to the right or left when the black cover/dial is turned. Once adjusted and set, the linkage will move to open the choke valve/blade when the bimetal coil is heated via the 12 volt current. It seems to me that the manifold-heated chokes make more sense since they are activated by the actual heat of the engine. Be that as it may, my electric choke should still work... but it doesn't. Let me know if you still need a photo and, if so, I will take the choke apart in the morning and post a photo or two.

Roger (50141)

[Clem Z.]

Re: Edelbrock Electric Choke Issue

Clem,
The spring has a "hooked" end that latches on to a short post/stud which is attached to the linkage piston. The post moves to the right or left when the black cover/dial is turned. Once adjusted and set, the linkage will move to open the choke valve/blade when the bimetal coil is heated via the 12 volt current. It seems to me that the manifold-heated chokes make more sense since they are activated by the actual heat of the engine. Be that as it may, my electric choke should still work... but it doesn't. Let me know if you still need a photo and, if so, I will take the choke apart in the morning and post a photo or two.

Roger (50141)

maybe you don't have a choke problem because the choke should go wide open in 1- 2 minutes,depends on the temp.. if you still have the problem after that length of time i would say it is not the choke. the carb may be too lean or the wrong springs in the power pistons for your application. you can just keep tightening up,going richer on the choke causing it to stay part way closed longer till the problem goes away and as long as the choke opens all the way once it is hot that may solve your problem. if you tighten the spring too far the choke may not open all the way.

[Roger P.]

Re: Edelbrock Electric Choke Issue

maybe you don't have a choke problem because the choke should go wide open in 1- 2 minutes,depends on the temp.. if you still have the problem after that length of time i would say it is not the choke. the carb may be too lean or the wrong springs in the power pistons for your application. you can just keep tightening up,going richer on the choke causing it to stay part way closed longer till the problem goes away and as long as the choke opens all the way once it is hot that may solve your problem. if you tighten the spring too far the choke may not open all the way.

Clem,
I had the carburetor adjusted by a carburetor shop when I bought the car over 2 years ago (hard to find carb shops these days!). About 1 year ago, I had a Corvette specialist mechanic do some work on my car and he changed the jets, etc. since it was running too rich. The carb is a 750 cfm, and I understand that a 600 cfm is really better for a small block. However, he told me that it would be fine with the new smaller jets. Again, it runs great once it warms up, but the stumble on acceleration when cold is really annoying. The issue that I am having is that I am unable to move the choke valve/blade in the airhorn when trying to adjust the choke with the black cover/dial. Do I need to adjust the linkage by bending the small linkage connecting rod? That is the only thing that I can see as being the reason why the choke won't close enough, and therefore why it won't stay on long enough. Does this make sense to you? When I manually move the linkage piston, the choke valve/blade fully opens & closes. Can I physically watch the choke coil expand by holding the black cover/dial in my hand with the ignition key turned on to make sure that the electric choke mechanism is working?

Thanks for your help,
Roger (50141)

[Clem Z.]

Re: Edelbrock Electric Choke Issue

Clem,
I had the carburetor adjusted by a carburetor shop when I bought the car over 2 years ago (hard to find carb shops these days!). About 1 year ago, I had a Corvette specialist mechanic do some work on my car and he changed the jets, etc. since it was running too rich. The carb is a 750 cfm, and I understand that a 600 cfm is really better for a small block. However, he told me that it would be fine with the new smaller jets. Again, it runs great once it warms up, but the stumble on acceleration when cold is really annoying. The issue that I am having is that I am unable to move the choke valve/blade in the airhorn when trying to adjust the choke with the black cover/dial. Do I need to adjust the linkage by bending the small linkage connecting rod? That is the only thing that I can see as being the reason why the choke won't close enough, and therefore why it won't stay on long enough. Does this make sense to you? When I manually move the linkage piston, the choke valve/blade fully opens & closes. Can I physically watch the choke coil expand by holding the black cover/dial in my hand with the ignition key turned on to make sure that the electric choke mechanism is working?

Thanks for your help,
Roger (50141)

you need a ground to make the heater work. remember the fast idle cam will prevent the choke butterfly from moving unless you hold open the throttle some.

[Timothy B.]

Re: Edelbrock Electric Choke Issue

Roger,

Read this owners manual for your carburetor. I think the first problem is the carburetor is to big for the engine and the fuel signal is weak so the main circuit is delayed (stumble) because of this.

The choke adjustment is performed by setting the choke pull off (vacuum piston) first, you can use a paper clip to perform this. After that, check that the fast idle cam is on the correct step and adjust linkage if needed. Finally, set the black coil to the proper index mark as indicated by the instructions.

If you suspect the coil spring is out of calibration, the proper adjustment is made at 68* temperature and the coil is turned so that the choke just barely closes at this temp.



http://www.edelbrock.com/automotive_...ers_manual.pdf

[Stuart F.]

Re: Edelbrock Electric Choke Issue

I'm not too familiar with the Edelbrock Electric choke, but it is similar to the unit I have on my AFB. I tapped into a 12volt ignition switched power source on my windshield wiper motor (easiest and closest source). My ground goes to a Thermal sensor I have bolted to my intake manifold (don't believe Edelbrock uses that). But the bimetalic spring sounds like the same and does have a loop on the end to engage the pulloff piston tang. The advantage of this is that it both pushes and pulls the piston (closes and opens the choke), unlike the standard hot air mechanism spring which only pushes the tang and relies on the vacuum suction on the piston to open the choke. The fault with the old AFB choke was that the pulloff piston would bind due to build up of white corrosion and the extra heat and fuel vapors over time gumming up and/or warping the choke housing.

I believe Tim is right that you have too much carburetor on that car to begin with. What with today's gas making it difficult to tune out hesitation and stumble as it is, you have an exasperated problem that may be further messed up by a "carburetor specialist". It took me a long time to tune out those problems on my AFB, and it involved a lot of trial and error on my part; different primary jets and metering rods, venturi clusters (air bleeds), and a different accelerator pump squirter. My electric choke, on the other hand, has eliminated the choke from the problem equation completely. It works remarkably well - very consistent, even after lengthy periods of non use. The car may set for 3 to 4 weeks at a time, and when I go to start it, the choke sets fully with one throttle kick and returns to full open at the appropriate time for the ambient conditions. BTW, my choke kit came from J.C. Whitney about 10 years ago and I only installed it about a year ago when I gave up trying to be 100% stock/original. What a relief.

Stu Fox

[Paul L.]

Re: Edelbrock Electric Choke Issue

This is an Edelbrock #1406 (600cfm) on my (former) 1967 327/300. The positive wire is connected to the ignition-switched 12V terminal on the ballast resistor and the ground to the metal body of the choke housing. It worked very well.

[Michael W.]

Re: Edelbrock Electric Choke Issue

[quote=Roger Piper (50141);528890 When I turn the black cover/dial from one extreme to the other (lean to rich) with the engine off, the choke valve/blade hardly moves at all. [/quote]

Until you resolve this issue, talk of jetting or carb size is not really of relevance. I'm not familiar with this exact config, but would imagine that if you remove the choke cover with spring and heater and move the mechanism manually, the binding or restriction will become evident.

[Stuart F.]

Re: Edelbrock Electric Choke Issue

I believe Clem has addressed some of the concerns and assumptions that Roger needs to make clear before anyone can give him pertinent advice, i.e. is he holding the throttle open enough to release the high idle linkage when he checks the choke blade movement.

We've all faced similar issues with carburetors over the years and know how to check them out. We then assume everyone else knows the same checks and procedures that we know and we look for some new problem to solve for them when in fact it is likely to be an old problem on which we are just failing to communicate a resolution.

Happy New Year

Stu Fox

[Stuart F.]

Re: Edelbrock Electric Choke Issue

Paul;

I was not addressing any comments at you or anyone else. I think you posted a great picture which can help people get a better idea what is being discussed. Sometimes it can a bit frustrating when you're trying to help someone without getting the complete picture of their situation. I admire service writers at dealerships for their patience and ability to ask the right questions to get to the bottom of the problem. Few of us are so gifted. Please don't stay mute. Sometimes the simplest of questions or comments are of the greatest help.

Stu Fox

[Roger P.]

Re: Edelbrock Electric Choke Issue

Good morning & Happy 2011,
Thank you all for your input. I found some binding of the choke valve/blade and, after some carb cleaner and massaging, got the binding issue resolved. I tested and installed the new choke cap/dial and the choke appears to be working fine now. Unfortunately, that didn't resolve my cold stumble/bog upon acceleration. Keep in mind that I live in South Florida, so it rarely gets really cold here. In fact, I don't use the Vette unless the temperature is at least in the mid 60's. Typically, it is in the mid 70's to low 90's (Stu, I'm sure you can relate). When I think about it, the only thing that the choke helps me with is increasing the idle which masks the stumble until the engine warms up to operating temperature. Being that the choke (fast idle) doesn't last very long, I am unable to compensate for the problem as the engine warms up. As a test, I set the idle to about 1600 rpm and didn't have any cold stumble upon acceleration. So it appears that there is a lean spot that needs to get resolved. I already moved the accelerator pump linkage closest to the carb with no change. Based on the Edelbrock manual that Tim sent me, it looks like I should try changing the metering rod springs to stronger springs. I also wanted to check for any vacuum leaks, but didn't want to spray carb cleaner around the engine as it could eat the paint. I know that propane is also used to check for vacuum leaks, but it sounds dangerous -- perhaps there is no danger since there isn't any spark?? Looking at Paul's photo, I was also curious if the hose from the PCV valve has to be tight at the fitting on the carb. My PCV hose doesn't have a hose clamp at the carb and doesn't fit very tight. Would this cause a vacuum leak? My carb has been on my car for about 20 years, so maybe it's time to replace the base and air horn gaskets which might also be leaking air?? What do you guys recommend at this point (before I replace the carb)?

Thank you,
Roger (50141)

[Clem Z.]

Re: Edelbrock Electric Choke Issue

make sure the heat riser valve on the exhaust manifold is working to force exhaust heat into the heat riser crossover in the intake manifold. this is very important if you have the cast iron intake manifold.

[Roger P.]

Re: Edelbrock Electric Choke Issue

make sure the heat riser valve on the exhaust manifold is working to force exhaust heat into the heat riser crossover in the intake manifold. this is very important if you have the cast iron intake manifold.

Clem,
For weekend cruising, I have a 350/345 HP GM Performance crate engine in my car (the original motor is stored on an engine stand in a warehouse). I purchased the car with this configuration. Based on my research, these are the specs. for my engine: aluminum cylinder heads similar to those used on the L98 Corvette engine, a Z28 high-rise dual-plane aluminum intake manifold, hypereutectic 9.8:1 pistons, forged crank and rods, and a single-pattern 235-degree hydraulic camshaft with 0.480-inch lift. Other information found says the motor has a hydraulic roller cam 235*/235* @ 0.050" tappet lift, 0.480"/0.480" theoretical valve lift, ground on 114* lobe separation angle, and pressed-pin flat-top hypereutectic pistons. I have limited mechanical knowledge, so I'm sure you will understand much more of what this means than I do. Do I still need the heat riser valve and, if so, where would I find it on the exhaust manifold to check it? There is a small nipple/port on the passenger side manifold that isn't connected to anything. I was also wondering if my fuel filter is located too close to the head (touching at one spot). I attached a few photos so you can see my engine set-up.

Roger (50141)